The high-temperature P2/c(1)-C2/c phase transition in Fe-free Ca-rich P2(1)/c clinopyroxenes

M Tribaudino*, F Nestola, C Meneghini, GD Bromiley

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

An in situ, high-temperature, powder diffraction investigation was performed for iron-free clinopyroxenes with compositions Ca0.40Mg1.60Si2O6, Ca-0.52 Mg1.46Al0.05Si1.98O6, Ca0.59Mg1.41Si2O6 and Ca-0.70 Mg1.30Si2O6, up to 850degreesC using synchrotron radiation (ESRF, Grenoble). In samples with compositions Ca0.52Mg1.46Al0.05Si1.98O6 and Ca0.59Mg1.41Si2O6, evidence of for the P2(1)/c-C2/c displacive phase transition was seen in changes in lattice parameters at T approximate to 550 and 300degreesC respectively. Landau modelling of the phase transition behaviour for the sample with composition Ca0.52Mg1.46Al0.05Si1.98O6 shows a tricritical behaviour [T-c = 547(16)]. Comparison with the transition behaviour in other samples with lower Ca contents along the join diopside-enstatite indicates that a decrease in T-c, and a switch from first-order to tricritical behavior occurs with increasing Ca content. The change in the transition behaviour was related to an interaction with the antiphase domains at the nanoscale.

Original languageEnglish
Pages (from-to)527-535
Number of pages9
JournalPhysics and Chemistry of Minerals
Volume30
Issue number9
DOIs
Publication statusPublished - Oct 2003

Keywords

  • clinopyroxene, in situ HT powder diffraction synchrotron radiation
  • phase transition
  • thermal expansion
  • DIOPSIDE-ENSTATITE CAMGSI2O6-MG2SI2O6
  • HIGH-PRESSURE
  • THERMODYNAMIC PROPERTIES
  • C2/C
  • JOIN
  • CLINOENSTATITE
  • PIGEONITE
  • PYROXENES
  • BEHAVIOR
  • XRD

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